Fiber reinforced plastics resulting from compositing fiber materials and thermoplastic resins have come to be used in recent years in various products. Examples include, for instance, GFRPs and CFRPs, in which glass fibers, carbon fibers or the like are composited with resins, and which are widely used in the fields of automobile parts, sports goods, housing materials, home appliances and the like. Articles obtained through compositing of such fibers exhibit excellent strength characteristics. However, the disposal methods resorted thereto in order to dispose of these articles are problematic, for instance, in that recycling is difficult, and in that a significant environmental burden is incurred.
Against this background, it is desirable for plastic composite materials to be lightweight and have excellent strength characteristics, and to be disposable at low cost, which translates into a small environmental burden. Cellulose fibers, which are abundant natural resources and have excellent strength characteristics, have attracted attention as reinforcing fibers that combine the above features, and are thus being actively researched.
Numerous research studies are being conducted on compositing of resins and cellulose nanofibers in which cellulose size is of the order of nanometers. Fiber diameters used ordinarily in papermaking, filter membranes and the like lie in a range of about 10 m to 50 μm. In cellulose nanofibers, on the other hand, fiber diameter is made 1/100 to 1/10,000 finer, down to the nanoscale; cellulose nanofibers are accordingly expected to bring out functions, such as reinforcement of resin crystals, different from those when ordinary fibers are used. As compared with conventional fiber-reinforced plastics, such fiber-reinforced plastics obtained through compositing of cellulose nanofibers and resins are expected to be applied to and further implemented in various products by bringing out a reinforcing function unknown as yet in conventional art while incurring a small environmental burden.
Herein Patent Documents 1 to 3 illustrated in the examples below were published for the purpose of using cellulose as a composite material.